Ipsapirone is an azopirone derivative that selectively interacts with serotonin-1A (5-HT1A) receptors and fails to affect other neurotransmitter receptors. In this study, ipsapirone at 15 mg or 30 mg was compared with diazepam at 15 mg and placebo in a double-blind, random assignment study design in patients with generalized anxiety disorder (GAD). During 4 weeks of treatment, both active drugs were therapeutically superior to placebo, without significant drug vs. drug therapeutic differences. The side-effect profile of ipsapirone at 15 mg was favorable compared to diazepam, but at 30 mg ipsapirone produced significant gastrointestinal disturbances.